Usually an exhaust gas treatment device, which for example is a catalytic converter or a particle filter, comprises a housing and at least one exhaust gas treatment element, such as for example a catalytic converter element or a particle filter element arranged therein. With usual design the housing has a jacket and an outlet funnel, while an inlet funnel can usually be present as well. The respective exhaust gas treatment element as a rule is arranged in the jacket of the housing with a bearing mat which envelopes the exhaust gas treatment element in the circumferential direction and axially supported on the housing via a support ring.
To reduce the thermal loading of an environment of the exhaust gas treatment device it is possible in principle to equip the outlet funnel with an air gap insulation, for the purpose of which the outlet funnel at least in certain regions is of a double wall design. For this purpose, the outlet funnel can comprise an outer funnel and an inner funnel between which an insulation space is formed.
Problematic with such an exhaust gas treatment device are the thermal expansion effects that occur in operation, which result in relative movements and thus in mechanical stresses of the component parts concerned. For example, the inner funnel in operation heats up faster than the outer funnel. In addition, the inner funnel can reach higher temperatures than the outer funnel. This results in a different heat expansion between outer funnel and inner funnel.